AD 2003-13-04

This AD becomes effective on August 15, 2003.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in the regulations as of August 15, 2003.

You may get the service information referenced in this AD from Pilatus Aircraft Ltd., Customer Liaison Manager, CH-6371 Stans, Switzerland; telephone: +41 41 619 63 19; facsimile: +41 41 619 6224; or from Pilatus Business Aircraft Ltd., Product Support Department, 11755 Airport Way, Broomfield, Colorado 80021; telephone: (303) 465-9099; facsimile: (303) 465-6040. You may view this information at the Federal Aviation Administration (FAA), Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 2003-CE-12-AD, 901 Locust, Room 506, Kansas City, Missouri 64106; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Doug Rudolph, Aerospace Engineer, FAA, Small Airplane Directorate, 901 Locust, Room 301, Kansas City, Missouri 64106; telephone: (816) 329-4059; facsimile: (816) 329-4090.

What Events Have Caused This AD?

The Federal Office for Civil Aviation (FOCA), which is the airworthiness authority for Switzerland, recently notified FAA that an unsafe condition may exist on all Pilatus Model PC-6 airplanes. The FOCA reports an incident where cracks have been found in the ribs of the inboard integral fuel tanks in the left and right wings of a Model PC-6 airplane. Investigation revealed that the cracks can occur when there are excessive pressure differentials between the ambient air pressure and that of the fuel tanks. The effect of this differential can be to compress the wing in the area of the fuel tank and cause distortion of the related structure. This distortion may result in fatigue cracks on ribs within the wing.

What Is the Potential Impact If FAA Took No Action?

These fatigue cracks on the ribs within the wing could lead to wing failure during flight.

Has FAA Taken Any Action to This Point?

We issued a proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to all Pilatus Model PC-6 airplanes. This proposal was published in the Federal Register as a notice of proposed rulemaking (NPRM) on April 4, 2003 (68 FR 16458). The NPRM proposed to require you to inspect the integral fuel tank wing ribs for cracks and the top and bottom wing skins for distortion, repair any cracks or distortion before further flight, and accomplish a fuel tank ventilating system installation.

Was the Public Invited To Comment?

The FAA encouraged interested persons to participate in the making of this amendment. We did not receive any comments on the proposed rule or on our determination of the cost to the public.

What Is FAA's Final Determination on This Issue?

After careful review of all available information related to the subject presented above, we have determined that air safety and the public interest require the adoption of the rule as proposed except for minor editorial corrections. We have determined that these minor corrections:

—Provide the intent that was proposed in the NPRM for correcting the unsafe condition; and

—Do not add any additional burden upon the public than was already proposed in the NPRM.

How Does the Revision to 14 CFR Part 39 Affect This AD?

On July 10, 2002, FAA published a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), which governs FAA's AD system. This regulation now includes material that relates to special flight permits, alternative methods of compliance, and altered products. This material previously was included in each individual AD. Since this material is included in 14 CFR part 39, we will not include it in future AD actions.

How Many Airplanes Does This AD Impact?

We estimate that this AD affects 35 airplanes in the U.S. registry.

What Is the Cost Impact of This AD on Owners/operators of the Affected Airplanes?

We estimate the following costs to accomplish the inspection:

We estimate the following costs for each rib to accomplish any necessary rib repair that will be required based on the results of this inspection. We have no way of determining the number of airplanes that may need such repair.

We estimate the following costs to install any inboard fuel tank vent system that will be required based on the results of this inspection. We have no way of determining the number of airplanes that may need such installation.

Does This AD Impact Various Entities?

The regulations adopted herein will not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.

Does This AD Involve a Significant Rule or Regulatory Action?

For the reasons discussed above, I certify that this action (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A copy of the final evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

Accordingly, under the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

1. The authority citation for part 39 continues to read as follows:

2. FAA amends § 39.13 by adding a new AD to read as follows: